To evaluate the feasibility of chest limit low dose CT in children using Philips iCT scanner as an example.

A total of 28 consecutive children aged between 1 month and 7 years (median age 8 months) who were claimed CT exam by clinicians and received limit low dose CT scans were enrolled. The limit low dose CT were undertaken on a 256-slice CT scanner (Brilliance iCT, Philips) with parameters as 80 kV, 10 mAs, 0.625 mm×128, and pitch=1. Firstly, lung algorithm group and standard algorithm group 4 mm slice-thickness image series were reconstructed with lung and standard algorithm respectively using iterative reconstruction (IR) algorithm (iDose⁴ 4). Then a series of 0.67 mm slice-thickness images were reconstructed with IR (iDose⁴ 4) and smooth A algorithm, and was transformed into transverse 4 mm images (image transformation group) and coronal multiple planar reformatted (MPR) and volume-rendered (VR) images along the central airway. The transverse images in above three groups were displayed in the same lung window for SD measurement and subjective image quality evaluation on a 5-point scale. The dose length product (DLP) was recorded and the effective dose (E) was calculated.

The SD values of lung algorithm group, standard algorithm group and image transformation group were 26.7±7.6, 15.1±5.5 and 16.7±4.9, respectively, which showed statistically significant difference (F=29.6, P<0.05). The noise of lung algorithm group was higher than those of standard algorithm group and image transformation group (mean difference values were 11.6 and 9.6, respectively, P<0.05), but there were no significant difference between standard algorithm group and image transformation group (P>0.05). All images had enough diagnostic image quality. The coronal MPR and VR images were helpful for interpretation of axial images. The mean DLP and E were (8.65±2.97) mGy·cm and (0.21±0.10) mSv, respectively. The lowest DLP and E were 4.40 mGy·cm and 0.08 mSv, respectively.

Using Philips iCT scanner as an example, chest limit low dose CT scanning was feasible for children. Combining with IR and image transformation, the image quality was fully guaranteed and 3D images increased diagnostic confidence.

Low-dose CT; Children; Chest; Iterative reconstruction algorithm; Radiation dose